The five-time champion recovered from her stumble at the start Tuesday and defeated Stefanie Voegele 6-3, 6-2.
It was Williams first appearance on Centre Court since the 2008 final, when she beat sister Serena for her second Wimbledon title in a row.
Venus tumble was one of several wobbly moments as she began her bid for a three-peat. She double-faulted in the opening game and had to erase two break points. She was passed the first two times she reached the net. She slipped and nearly fell a second time.
Then Williams found her footing, winning 14 consecutive points to help take a 5-1 lead. She had another spurt in the second set after losing serve for 2-all, and swept the final four games.
Williams improved to 51-4 at the All England Club since 2000, when she won the title for the first time. Shes seeded third but the tournament favorite with London bookmakers.
The new retractable roof again worked well, keeping rain away for a second successive day. Play began on a cloudless afternoon, prompting an official on the clubs public-address system to urge that fans use sun block.
Kimiko Date Krumm, a 38-year-old wild card who came out of retirement last year, lost in her first Wimbledon match since 1996 to No. 9-seeded Caroline Wozniacki, 5-7, 6-3, 6-1. Former No. 1 Jelena Jankovic beat Julia Goerges 6-4, 7-6 (0).
In mens play, No. 12 Nikolay Davydenko defeated Daniel Evans 6-2, 6-3, 6-3.
Serena Williams won her opening match Monday against qualifier Neuza Silva, 6-1, 7-5. Serena is seeded second and considered the biggest threat to Venus.
Serena said she draws confidence from projections shell be playing in the final a week from Saturday.
I always feel like if people can believe in me, then I should, too, she said. I always think about how I feel when other people that are top seeded are playing. Im like, OK, theyll win. So I feel like I should feel that way about myself as well.
Against the No. 154-ranked Silva, Serena lost only nine points on her serve, but converted only one of five break-point chances in the second set and struggled to close out the win.
I could have played a ton better, especially on key points, Williams said. Thats a usual feeling for me from first round to the finals. Im really insatiable. I always want more.
Serenas second-round opponent Wednesday will be Jarmila Groth, who is ranked 69th. Williams won when they met at the Australian Open in 2008 but had to search her memory when asked about Groth, who recently changed her last name.
Williams conceded its difficult to remember whos who on the womens tour.
I just know the standard: Everyone is from Russia, Williams said jokingly. Sometimes I think Im from Russia, too. I feel like, you know, OK, all these new ovas ... I think my name must be Williamsova.
Groth is actually from Australia, but five of the 10 highest-ranked women are Russians. Two others are named Williams.